Abstract: The microsporogenesis,megasporogenesis,the development of male gametophyte,female gametophyte,embryo and endosperm,and double fertilization of Conyza canadensis(L.) Cronq were studied in this paper.The results show as follows:the anther is tetrasporangiate and its mature wall comprises of an epidermis,endothelium,a middle layer and a single-layered tapetum;the epidermis degenerates;cells of endothelium persisted are columnar and with fibrous thick walls;the middle layer degenerates early and only a vestige can be observed at meiosis-I of microsporocyte;the tapetum belongs to glandular type,generally,is out of shape and degenerates early at meiosis-I of microporocyte;cytokinesis in the microsporocyte meiosis is of the simultaneous type,and the microspore tetrads are tetrahedral or isobilateral;pollen grains are mainly 3-celled,and occasionally 2-celled;the ovary is bicarpellate,unilocular,one ovules and basal placenta;the ovule is unitegmic,tenuinucellate,anatropous and with developed endothelium;archesporial cell of megaspore differentiates immediately below the nucellar epidermis and functions as megasporocyte after development,and then,the megasporocyte undergoes meitotic to form a linear tetrad,only one chalazal megaspore in linear tetrad becomes the functional megaspore;the embryo sac is of the Polygonum Type;two polar nuclei melt into a secondary nuclei before fertilization;fertilization is porogamous;the development type of the endosperm is Nuclear Type,and the embryogeny belongs to the Asterad Type;endosperm haustorium is present.